Max, To echo the other posts, you do have a very rare and desireable rifle. The"720" is the action patent use number. Your rifle is the 720th Gibbs Farquharson made. The numbers go to 974 the last one made in 1910. Your rifle is not listed in Kirtons book, however number 709 is, and also has Selous plates as do 749, 766, and 770. these were used on a fair number of sporting rifles until near the end of production. 709 is the lowest number with these plates known by Kirton. Gibbs records were lost during WWII, so listed rifles are "reported" examples.
Depending on the ammount of original finish and bore condition your rifle could be worth between 7 and 12 thousand dollars.
The .461 Gibbs cartridge had a good following for target work as well as a hunting round.
All the best, Mal
